General Sherman is a giant sequoia (Sequoiadendron giganteum) located in the Giant Forest of Sequoia National Park in California. By volume, it is the largest known living single stem tree on Earth. [source]

General Sherman isn’t the tallest known living tree on Earth (that distinction belongs to the Hyperion tree, a Coast redwood), nor is it the widest (both the largest cypress and largest baobab have a greater diameter), nor is it the oldest known living tree on Earth (that distinction belongs to a Great Basin bristlecone pine). However with a height of 83.8 metres (275 ft), a diameter of 7.7 metres (25 ft), an estimated bole volume of 1,487 cubic metres (52,513 cu ft), and an estimated age of 2,300–2,700 years, it is among the tallest, widest and longest-lived of all trees on the planet. [source]

The Crannell Creek Giant, a coast redwood (Sequoia sempervirens) near Trinidad, California, is the largest tree known to humans and is estimated to have been 15 to 25% larger than General Sherman by volume. Unfortunately the tree was cut down in the mid-1940s. [source]

The tree was named after American Civil War general, William Tecumseh Sherman, in 1879 by naturalist James Wolverton, who had served as a lieutenant in the 9th Indiana Cavalry under Sherman. In 1931, following comparisons with the nearby General Grant tree, General Sherman was identified as the largest tree in the world. One result of this process was that wood volume became widely accepted as the standard for establishing and comparing the size of different trees. [source]